K/9 Calculator
K/9 and BB/9 put strikeouts and walks on a per-nine-innings scale so starters and relievers compare fairly, while K/BB captures pure strikeout-to-walk dominance.
How it works
K/9 = 9 × strikeouts ÷ innings pitched, and BB/9 uses the same formula with walks. K/BB is simply strikeouts divided by walks and has no innings term. Enter innings in baseball notation (6.2 = 6⅔) and all three update together.
Worked example
70 strikeouts and 20 walks over 68⅓ innings: K/9 = 9 × 70 ÷ 68.333 = 9.22, BB/9 = 9 × 20 ÷ 68.333 = 2.63, and K/BB = 70 ÷ 20 = 3.50.
Frequently asked questions
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Sources
- MLB.com — Strikeouts Per Nine Innings
- MLB.com — Standard & Advanced Stats Glossary
- FanGraphs — Sabermetrics Library
- Baseball Reference — Glossary
Last reviewed March 1, 2025. Rules and manufacturer charts change — verify against current official sources each season.